1. Field of the Invention
The present invention relates to an apparatus for resetting a physical channel in a wireless communication system, and more specifically to a method for resetting a physical channel performed when communication status is changed between a mobile station and a radio network controller in a mobile communication system having a technology of wideband code division multiple access (W-CDMA).
2. Description of the Related Art
Relating to a method of assigning a common communication channel in a UMTS (universal mobile telecommunications system), a message, an algorithm, etc. to be used in a 3GPP (3rd Generation Partnership Project) are recommended. Generally, an individual channel as a physical channel specific to each mobile station (MS) is activated by a trigger of a mobile station in an idle status transmitting a connection request, or calling an MS in an idle status from a network.
When the individual channel is activated, each of the mobile station, the base transceiver station (BTS), and the radio network controller (RNC) forming part of a wireless network determines various parameters according to various types of information such as a requested circuit class, line speed, etc. and activates the line.
Relating to a packet communication, a status of assigning an individual channel and performing a packet communication, and a status of using a common channel as a physical channel common among a plurality of MSs and performing a packet communication are defined. The former is referred to as a Cell_DCH (dedicated channel) status, and the latter is referred to as a Cell_FACH (forward access channel) status.
The MS and the RNC determine the communication status to be used mainly based on the line use rate. For example, the MS can use the Cell_DCH status when the line use rate is high (when there is a large amount of data communication). In this case, for example, an individual channel line of a fix rate of 384 kbps is continuously used.
On the other hand, when the line use rate is low (when there is a small amount of data communication), the MS temporarily releases an individual channel line, the status is changed to the Cell_FACH status, and the minimal data transmission/reception is performed in the common channel line (FACH: DL (downlink), RACH: UL (uplink)). When the line use rate in Cell_FACH increases (when the amount of data communication increases), the individual channel line is re-activated (reset) again.
As described above, when an individual channel is activated from the idle status and a transition is performed between an individual channel and a common channel, it is necessary to set various parameters relating to setting a channel of an Iub line between the RNC and the BTS and a Uu line between the MS and the BTS when an individual channel is set. At this time, the parameter of the Iub line is set using an NBAP signal (node B application part) as a control signal between the RNC and the BTS, and the parameter of the Uu line is set using an RRC (radio resource control) signal as a control signal between the RNC and the MS.
FIG. 1A shows the basic operation sequence of activating an individual channel when a call is issued in the idle status in the conventional UMTS system. The individual channel is constituted by a DCCH (dedicated control channel) and a DTCH (dedicated traffic channel).
First, the MS transmits a call connection request 11 to the RNC. In response to the request, the RNC communicates messages 12 through 15 with the BTS, and communicates messages 16 and 17 with the MS. Thus, the DCCH resource is activated.
Then, procedures 18 through 20 are performed with the MS, BTS and the RNC, and the CN (core network) not shown in the attached drawings.
Next, messages 21 through 25 are communicated among the MS, BTS, and RNC, and the DTCH resource is activated. After a procedure 26 is performed, the connection of the individual channel line is connected.
FIG. 1B shows the basic operation sequences of the transition from a Cell_DCH to a Cell_FACH and the recovery from the Cell_FACH to the Cell_DCH.
While the communication is being performed along the Cell_DCH, the MS and the RNC performs a procedure 31, and the line use rate is monitored. When a line use rate lower than a threshold is detected in an event 32, the MS transmits to the RNC a message 33 of a measurement report event 4b requesting the transition to the Cell_FACH.
In response to the request, messages 34 through 38 are communicated between the MS and the RNC, and messages 39 through 44 are communicated between the BTS and the RNC. Thus, the individual channel line is released, and the system passes control to the Cell_FACH.
Next, when a line use rate exceeding the threshold is detected again in an event 45, the MS transmits to the RNC a message 46 of a measurement report event 4a requesting the reset of the individual channel line. In response to the request, messages 47 through 52 are communicated between the BTS and the RNC. At this time, the RNC transmits to the BTS the message 47 (radio link setup request) via the NBAP signal, and notifies the BTS of the values of various parameters required to additionally activate the DCCH and the DTCH.
Next, the RNC transmits to the MS a message 53 (transport channel reconfiguration) via an RRC signal, and notifies the MS of the values of various parameters required to activate the DTCH.
The MS performs a recovery operation 54 from the Cell_FACH to the Cell_DCH using a transmitted parameter, and transmits a message 55 to the RNC. Thus, the system recovers to the Cell_DCH. The messages 39 through 55 are communicated along the Cell_FACH.
FIGS. 2A and 2B show the contents of the message 47 prescribed by the 3GPP TS25.433. An IE/Group Name is a parameter name, and “Presence” indicates the types of M (mandatory), O (optional), and C (conditional).
FIGS. 3A through 3D show the contents (parameter) of the message 53 prescribed by the 3GPP TS25.331. Information Element/Group Name is a parameter name, and “Need” indicates the types of MP (mandatorily present), MD (mandatory with default value), OP (optional), and CH (conditional on history).
Aside from the Cell_FACH, the Cell_PCH (paging channel) and the URA (UTRAN registration area)_PCH are prescribed. At the recovery from these communication statuses to the Cell_DCH, a parameter is reset using a message among the MS, BTS, and RNC.
The following patent document 1 relates to a mobile communication system for setting the status of a mobile station by a base station notifying the mobile station of transmission/reception status update information.
The following patent document 2 relates to a communication system for performing data communication using the same logical line as in making the first connection according to the line connection related information about the logical line at the first connection.
The following patent document 3 relates to a mobile communication terminal for selecting the optimum communication system from among a plurality of communication systems according to the information corresponding to the target use specified by a user and setting corresponding communication software.
[Patent Document 1] Japanese Published Patent Application No. 2004-147050
[Patent Document 2] Japanese Published Patent Application No. 2003-051855
[Patent Document 3] Japanese Published Patent Application No. 2005-198082
In the conventional UMTS system, it is necessary for the RNC to notify the BTS and MS of all parameter required to activate the channel of the Cell_DCH for the recovery from the Cell_FACH to the Cell_DCH using a message. There are a large number of parameters as shown in FIGS. 2A through 3D. Therefore, when an individual channel is connected again, it takes a long time to set the parameters as well as to issue a call from the idle status.
Especially, when the MS performs a status change during the communication in a new mobile communication system in which IP-voice (VoIP) and IP-video are transmitted in real time, it is considered to be necessary to suppress the parameter setting time within, for example, several hundred milliseconds. Therefore, at the recovery from the Cell_FACH to the Cell_DCH, it is desired to minimize the number of parameters to be reset.